The first 70 semiconductor Auger processes

World Abstracts on Microelectronics and Reliability for larger batches and slice sizes. It was found that under optimized conditions of gas flow, deposition temperature and silane concentration, layers virtually free from stacking faults can be grown at a rate of about 0.25 micron per minute. InP/Langmuir-film m.i.s.f.e.t.G.G. ROBERTS, K. P. PANDE and W. A. BARLOW. Solid-St. Electron Devices 2, (6) 169 (November 1978). The electrical properties of m.i.s, structures based on indium phosphide and organic films deposited using the Langmuir-Blodgett technique have been investigated. A stronglyinver ted low-frequency C~ V response occurs at approximately 30 Hz using both melt-grown InP single crystals and epitaxial layers of this material prepared using the vapour-phase technique. Interface state distributions have been evaluated from the admittance data using quasistatic and conductance techniques. For an n-type InP-epitaxial-wafer/cadmium-sterate junction the effective surface-state density is found to be ~3 × 1011 cm 2 eV over a large fraction of the bandgap. Average surface-state densities calculated for structures based on melt-grown crystals were approximately one order of magnitude higher. For the first time measurements are reported for a transistor incorporating a Langmuir-Blodgett film. From the transfer characteristics of this relatively simple depletion-mode device the InP field-effect surface mobility is calculated to be 2250cm zV-~ s-~. Threshold voltage of m.o.s, transistors doped nonuniformly near the surface. HELMUT FELTL. Solid-St. Electron Devices 2, (6) 191 (November 1978). Due to impurity redistribution and ion implantation, m.o.s, transistors are usually doped nonuniformly beneath the gate. From an analytical solution of Poisson's equation a modified expression for the threshold voltage has been derived. The change in the impurity concentration is taken into account, on the one side, in the usual manner by its contribution to the surface charge and, on the other side, on the basis of its contribution to the surface potential instead of the rather arbitrary approximation by an "'effective" impurity concentration. The modified formula gives a better description of the measured threshold voltages at least for an extended region, if not for the entire range of the applied substrate bias voltage. As theoretically predicted, the substrate bias coefficient corresponds to the bulk impurity concentration. A comparison with experimental results shows exceptionally close agreement if the depletion layer fully, or largely, covers the region of altered impurity concentration. If this region extends substantially beyond the depletion layer, deviations are observed. This result has been confirmed from impurity profiles determined for the purpose of verification. Resonant tunneling via localized impurity states in metalinsulator-metal junctions. N. DE S. CHRISCENSENand N. E. CHRISTENSEN. Solid St. Commun. 27, 1259 (1978). Strongly temperature dependent peaks in the tunnel conductance of AI A1 oxide Pd diodes appearing at low temperatures are interpreted in terms of resonant tunneling via impurity states. Such structure was not observed when non-transition metals (Ag, Au, Pb, Sn) were used as counter electrodes. Direct gap recombination in germanium at high excitation level and low temperature. WERNER KLINGENSTEIN and HEINZ SCHWEIZER. Solid-St. Electron. 21, 1371 (1978). In highly excited germanium and at low temperatures, a luminescence is observed at energies above the indirect gap at an energy of 0.880 eV. This luminescence is generally observed in connection with a broadened electron-hole-drop emission line thus indicating an increased density in the plasma state. At the same time, absorption in that energy range is reduced drastically. This luminescence is attributed to direct recombination processes between the F2 conduction band minimum and the F25 valence band maximum.

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The measurements we report concern the dependence of this luminescence on excitation conditions keeping the bath temperature constant at 2 K. Line-shape, line-width and energetic position indicate that free carrier band-to-band recombination and no excitonic effects are involved. The dependence of the luminescence intensity on excitation power is well explained by a coupling by Auger processes between the indirect and the direct gap in germanium. Thermal oxidation of silicon using triehloroethylene. R. SCOT CLARK. Solid St. Teclinol. p. 80 (November 1978). Trichloroethylene has been shown to be an effective source of C1 to be used during the thermal oxidation of silicon for integrated circuit manufacture. It has the same oxide gettering and device improvement characteristics as those of HCI oxidation: however, the benefit of TCE in high volume device manufacturing is the ease of handling and the lack of corrosiveness. These benefits are complimented by using the proven manufacturing "Plug-In'" bubbler packaging concept with its inherent disposal characteristics. Silicon epitaxy. MARTIN L. HAMMOND. Solid St. Teehnol. p. 68 (November 1978). Epitaxial silicon reactors have been relatively quiet workhorses in the semiconductor industry for approximately 10 years, with regular improvements being made in productivity, uniformity, and equipment reliability. Productivity increases in recent years have not been great; however, new developments in the radiant heating technique in combination with reduced pressure operation have led to some exciting new possibilities. A review of epitaxial silicon processes is presented with commentary on the interaction of theory and practice in new equipment concepts. Surface-induced valley-splitting in n-Channel (001) SiliconMOS charge layer. M. NAKAYAMAand L. J. SHAM. Solid St. Commun. 28, 393 (1978). The surface-induced valleysplitting theory by Sham and Nakayama is shown in the special case of a two-band model for the silicon band structure to be closely related to the electric break-through effect of Ohkawa and Uemura. Recent criticisms of our theory by Ohkawa are shown to be erroneous. The first 70 semiconductor Auger processes. P. T. LANDSBERG and D. J. ROSBINS. Solid-St. Electron. 21, 1289 (1978). Ten basic Auger recombination processes are considered: two phononless and two phonon-assisted band-band processes, four processes involving one type of trap and two donor-acceptor processes. Expressions are obtained for the recombination coefficient by making a constant matrix element approximation, working out the impact ionization rate, and using detailed balance, noting that impact ionization is the inverse process of the Auger effect. Assuming all bands involved (excepting the band which contains the impact ionizing carrier) to be parabolic, described by a diagonalized effective mass tensor, new results for eight of the ten cases are found. Different band structure types lead to a multiplicity of each of the ten processes, yielding seventy different types. They are classified by utilizing recent work on impact ionization thresholds as van Hove singularities. Processes involving excitons, pairs of particles bound to the same centre, etc. are not included here and add further Auger-type processes. On the multiphonon capture rate in semiconductors. BRIAN K. RIDLEY. Solid-St. Electron. 21, 1319 (1978). In the single-frequency approximation the multiphonon capturerate into a localized state is characterized by the HuangRhys factor S. How S depends upon the energy depth of the trap and the charge on the centre is illustrated in the context of quantum-defect wavefunctions, and two types of electron-phonon coupling: deformation and polar with